How about visitng our closest delta, see some birds, go for km on bikes, see planes take off, land, dance on the beach, go for a swinm, see some turtles, eat a paella and all right next to the city.
Yes the delta of the llobregat where the airport is located.
A fascinating unknown area of the city
How to get there?
Well from Hostal Australia, take the train to el Prat ( 10 km) and walk or rent a bike. You have a train every 10 minutes.
And after all the hard work head down to the beach for a paella.
Enjoy your day.
For more info look up: http://www.deltallobregat.cat